In the art of casting concrete pipe and concrete manhole risers, bell and spigot joints with O ring seals set in grooves in the spigot are much used to connect each separate element into a continuous sealed conduit or manhole.
However, it has long been a problem to produce a spigot with a true truncated conical circumferential outer face and having a true sealing groove, of uniform dimensions, extending annularly around that face because of flats, bumps, or slumps in the recently cast spigot portions.
It has heretofore been proposed, as in U.S. Pat. No. 2,984,886 to Jensen of May 23, 1961, to provide a circular skirt supported by rollers on the end face of an upended pipe, and rollers in contact with the outer face of the spigot, for centering a rotatable tool having blades for cutting a sealing groove around a "green" spigot and blades for chamfering the inner peripheral edge of the spigot. This device is hand turned, it accommodates only one size of spigot, and it does not grind the outerface of the spigot.
It has also been proposed, as in U.S. Pat. No. 4,109,635 to Rossborough of Aug. 29, 1978, to provide an assembly which rests on the end face of an upturned spigot and is centered on the longitudinal central axis thereof by manually adjustable internal and external guides. The outer face of the spigot and the sealing ring groove in the outer face are ground simultaneously by the same rotary cutter working on one side of the central axis as it progresses around the tracks of the assembly.